HomeNewsOn This Day in Test HistoryArticle Display - Test History

September 8, 1999: Helios Unmanned Vehicle Prototype Testing


The Helios prototype Unmanned Aerial Vehicle made its first flight. The unmanned flying wing spanned 247 feet and was designed ultimately to reach 100,000 feet and to fly missions lasting four days or more. The first flight of the Helios was cut short when an emergency parachute accidentally deployed, forcing the aircraft into a slow turn until it could be landed remotely. The Remotely Piloted Vehicle  was developed by AeroVironment Inc. as part of the National Aeronautics Space Administration’s Environmental Research Aircraft and Sensor Technology program.

The Environmental Research Aircraft and Sensor Technology program was a NASA program developed cost-effective, slow-flying unmanned aerial vehicles that can perform long-duration science missions at altitudes above 60,000 feet. The project included a number of technology development programs conducted by the joint NASA-industry ERAST Alliance. The project was formally terminated in 2003.  

The NASA Centurion was modified into the Helios Prototype configuration by adding a sixth 41 feet (12 m) wing section and a fifth landing gear and systems pod, becoming the fourth configuration in the series of solar-powered flying wing demonstrator aircraft developed by AeroVironment under the ERAST project. The larger wing on the Helios Prototype accommodated more solar arrays to provide adequate power for the sun-powered development flights that followed.The aircraft's maiden flight was on September 8, 1999.

The ERAST program had two goals when developing the Helios Prototype: 1) sustained flight at altitudes near 100,000 feet (30,000 m) and 2) endurance of at least 24 hours, including at least 14 of those hours above 50,000 feet . To this end, the Helios Prototype could be configured in two different ways. The first, designated HP01, focused on achieving the altitude goals and powered the aircraft with batteries and solar cells. The second configuration, HP03, optimized the aircraft for endurance, and used a combination of solar cells, storage batteries and a modified commercial hydrogen–air fuel cell system for power at night. In this configuration, the number of motors was reduced from 14 to ten.

Using the traditional incremental or stairstep approach to flight testing, the Helios Prototype was first flown in a series of battery-powered development flights in late 1999 to validate the longer wing's performance and the aircraft's handling qualities. Instrumentation that was used for the follow-on solar-powered altitude and endurance flights was also checked out and calibrated during the initial low-altitude flights at NASA Dryden

According to NASA, "ERAST was a multiyear effort to develop the aeronautical and sensor technologies for a new family of remotely piloted aircraft intended for upper atmospheric science missions. Designed to cruise at slow speeds for long durations at altitudes of 60,000 to 100,000 feet, such aircraft could be used to collect, identify, and monitor environmental data to assess global climate change and assist in weather monitoring and forecasting. They also could serve as airborne telecommunications platforms, performing functions similar to communications satellites at a fraction of the cost of lofting a satellite into space.